Air circulator and heater



May 8, 1951 Filed Sept. 6, 1946 5. c. WAHLBERG AIR CIRCULATOR AND HEATER 5 Sheets-Sheet 1 INVENTOR.

ERIC C. WAHLBERG y 3, 1951 E. c. WAHLBERG AIR CIRCULATOR AND HEATER 3 Sheets-Sheet 2 Filed Sept. 6, 1945 INVENTOR.

1531c c. WAHLBERG BY May 3, 1951 E. c. WAHLBERG 2,552,470

AIR CIRCULATOR AND HEATER Filed Sept. 6, 1946 3 Sheets-Sheet a g 68 INVENTOR. so 4 67 ERIC 0. WAHLBERG E F69 BY Patented May 8, 1951 UNITED STATES PATENT OFFICE AIR CIRCULATOR AND HEATER Application September 6, 1946, Serial No. 695,337

9 Claims.

This invention relates to air circulators and heaters. While certain aspects of the inventive concept may be broadly applicable to numerous types of such devices, the invention is particularly adaptable to self-contained portable, domestic devices utilizing electrical energy.

The prior art includes a great variety of air circulators, a large portion of which are arranged in combination with heat exchange devices and in many instances the controls are such that the circulator may be used without energizing the heating device. Such devices thus partake of a year round utility, being operable as a simple fan or air circulator in warm weather and as an air circulating heater during seasons of lower temperature. The present invention likewise embraces this desirable feature to which no claim for novelty is made. The present invention, however, embodies numerous original and improved features relating both to air circulating per se and to heating which distinguishes it from prior devices in this general field.

With relation to air circulation itself, irrespective of whether heating of the air is or is not accomplished, the more common devices for this purpose consist in simple multi-bladed fans which are generally more or less exposed. Such devices while in operation, present a continual hazard, the fan blades being either fully exposed or shielded only by open screens through which injurious articles may enter. With children the de sire to touch the visible rotating fan is such that the devices may properly be listed in the category of attractive nuisances.

Air impellers of the above type, as well as such devices wherein the impeller is more fully shielded have a further undesirable quality in that the air flow induced thereby is seldom if ever an even unidirectional flow, but such devices commonly produce turbulence, eddy currents and back pressures and extraneous air (unheated in the case of combined heaters) is entrained in the air flow.

Among the objects of the invention is to overcome the above undesirable characteristics of air circulators of the prior art.

Respecting heaters now commonly in use such instrumentalities frequently depend upon the outward propagation of radiant heat from incandescent resistance elements for all or a substantial portion of their heating effectiveness.

One familiar form of heater now in common use comprises a resistance element mounted at the center of a circular concave reflector. In such a device rays may be directed towards the person or object to be heated, but the intermediate air remains unheated by the rays passing therethrough. While the directional characteristics of such heaters are advantageous they present exposed heating elements which constitute fire hazards and, like the rotating fans, are a constant temptation to children. Furthermore, the use of such a device is not at all times very efficient, since the radiations may frequently impinge on heat absorbing objects such as walls and furniture which are not intended to absorb the limited energy available.

Another commonly encountered domestic heater has a partially exposed and radiating resistance element, and an air circulator which directs a how of air past such element, thus heating the air by direct contact so that the air temperature is elevated in addition to the object or person receiving the radiation. In such a device the inefliciency of the first-mentioned heater is mitigated and the structures of such devices frequently decrease the fire and injury hazard referred to, but they are neither fully safe nor fully efficient and since the heating of the air reduces the temperature of the elements and hence their rate of radiation, such devices are not ideal as either radiant heaters or air heaters.

Other household heaters have been devised in which the heating element is within a water chamber of the radiator type, the surrounding air being heated by conduction and being circulated by convection currents. Such devices while quiet, safe, and efficient are necessarily slow in attaining the desired temperature and are of substantial weight and thus not readily portable, and in many instances their cost is relatively high.

The present invention seeks to provide a safe, efiicient, and inexpensive heater which avoids the inherent disadvantages of the heaters above referred to.

The preferred embodiment of the present inventive concept comprises a casing of substantially cylindrical form adapted for horizontal disposition on a supporting surface. One or more air inlets are provided, preferably by way of louvers in end plates for the casing, and an air outlet is shown as positioned intermediate the end plates and towards the upper portion of the housing.

Air propelling means in the form of a motorfan unit is provided. The present embodiment includes a centrally disposed motor having a pair of impellers mounted inwardly of the end members of the casing to draw air inwardly through the louvers and towards the motor, such air passing in heat transfer relation to the motor so as to avoid the necessity of separate motor cooling means and so as to utilize the heat generated by the motor.

An elongated circuitous and expanding air passage is formed within the casing by the use of a spirally wound wall or bafile member which surrounds the motor, forming a chamber therefor, and spirals outwardly to terminate adjacent the air outlet.

For heating the air in its passage through the air conduit thus formed, there is provided electrical resistance means mounted adjacent the concave side of the spiral wall. The spiral arrangement of the conduit is such that as air is forced through the passage it will tend to flow in greatest volume and velocity against the outer or concave wall, thus contacting the heating elements whereby the air will be most efficiently raised in temperature. It will also be noted that the close proximity of the heating elements to the concave wall will raise the temperature of the wall and thus by conductivity raise the temperature of the opposite face of the wall which constitutes the inner or convex surface of the adjacent convolution, thus utilizing to maximum efliciency the heat generated by the element.

Another feature of the arrangement of the heating element is that, while the element is strung in transversely extending runs in zig-zag fashion within the passage, the runs are more closely spaced as the passage progresses outwardly and increases in cross-sectional area and thus the heat dissipated by the element increases in proportion to the increased area of the passage and thus to the amount of air traversing any given run of heating element.

Another and extremelly important feature of the disposition of the heating element, is that the element is wholly confined within the convolutions of the wall or bafile so that no part thereof is visible through the air outlet or may be reached by the insertion of any straight element through the outlet. Since the primary type of heat generated by such resistance elements is radiant heat, which heat is effective only upon the object upon which its rays impinge, it is desirable to avoid external propagation of such radiations and this is accomplished by the complete enshroudment of the element, whereby the entire heat generated is transferred to the passing air without wastage by external radiation.

In addition to the above features, it will be noted that the present structural arrangement provides an attractive, simple, and efficient device which is wholly self-contained, readily portable, requires a minimum space, and is particularly suited to the demands of economic manufacture.

Further objects and advantages of my invention will be apparent from the following description considered in connection with the accompanying drawings which form a part of this specification, and in which- Fig. 1 is a perspective view of a heater in accordance with a preferred embodiment of the invention;

Fig. 2 is a longitudinally vertical section through the heater shown in Fig. 1;

Fig. 3 is a section taken on the line 3-3 of Fig 2;

Fig. 4 is a wiring diagram showing one method of connecting the motor, heating element, and switches; and

Fig. 5 is a wiring diagram showing an alternative electrical hook-up.

Referring more particularly to the drawings, Fig. 1 discloses the inventive concept carried out in one preferred embodiment in which the external housing constitutes a horizontally disposed substantially cylindrical body, air to be heated being drawn inwardly from the opposite ends of the body and being discharged from a centrally disposed outlet at the side and adjacent the top of the body.

This embodiment of the invention comprises a pair of similar end housings l6 and H, each of which is provided with a louvered central portion i2 which is here shown as a separate flanged stamping fitting into and engaging a flange of the end housing as shown at 13. The inner peripheral edges of the end housings ID and II are preferably formed with outwardly extending flanges 14 which constitut symmetrical ornamental spaced rings encircling the structure and which have the utilitarian function of receiving therein the ends l5 of a central generally cylindrical body portion Iii, which body portion is formed in one side wall thereof, towards the upper portion, with an outlet aperture H to which is secured an ornamental and protecting grill work 18 through which the heated air is discharged.

The end housings i!) and H are also provided with handle end securing members 59, within which are secured the ends of a longitudinally extending carrying handle 2i? disposed across the top of the structure. The handle end securing means also house switch devices, the actuating members 2| of which extend through the securing members to provide convenient means for manipulation of the switches. Through one of the end housings, here shown as the housing IO, there extends a suitable electric cord for supplying current to energize the air impelling and air heating devices hereinafter described.

The end members are also preferably provided with supporting means, such as struck out gliding domes 23 by means of which the device may be suitably maintained in spaced relation from its support.

In connection with the above-described structure, it will be understood that the parts above defined may be suitably assembled and secured by interfitting frictional contact, by riveting, spot welding, or like means, details of such means not being here specified since the invention is in no way limited thereto and the present concept contemplates the use of all such means or their equivalent.

The central cylindrical body portion 16 which is secured between the flanges M is shown as provided with spaced inwardly directed flanges 24 to which are secured, as by rivets 25, the terminal edge flanges 26 of fan casings 21. Casings 2'! are substantially cup-shaped, being provided with centrally disposed air inlet apertures 28 through which air is drawn from the louvers of the end portions #2. In addition to forming fan chambers 29, the casings 21 receive and support the end portions of a pair of cooperating cup-shaped members 39, the cylindrical walls of which are united to form a cylindrical body 3| by the interfitting relation indicated at 32.

The motor-fan unit includes a conventional small electric motor 33 which may be of A. C., D. C. or universal type. The motor shaft 3d extends through the motor and beyond the ends thereof and through the end walls of the members 30. On the ends of the shaft 34, beyond the members there are provided impeller or fan elements which are thus housed within the fan chambers 29 formed between the ends of members 30 and the fan casings 21. For cooperation with the driven impellers 35 there are mounted upon the external end walls of the members 30 fixed air guides 33 which direct the flow of air inwardly towards the motor 33.

It will be understood, of course, that the invention is in no way confined to the particular type of motor-fan unit herein illustrated and while numerous variations and modifications of the structure here depicted may be successfully substituted it has been found that the arrangement here shown is highly satisfactory in the present combination. The present fan and guide arrangement is common in the art of fans and blowers and it will be understood that air enters the center of the impeller 35, the blades of which force the air outwardly, while the fixed guides 36 return the air inwardly to pass through the central apertures of the members 33.

In the present construction it will be noted that the guides 36 are covered by a centrally apertured fixed plate 37, the members 3!), guides 35 and plates 31 being formed as a rigid construction. The plates 31, in addition to acting with the guides 36 to confine the air flow and direct it inwardly through the apertures 38 of the members 30, receive supporting bolts 39 which extend outwardly from the motor 33 and act as a support therefor. The bolts 39 are secured to the plates 31 by suitable nuts 40 or their equivalent. By

this arrangement it will be seen that the motor shaft 34 with its impellers 35 is floating with respect to the members 30 and the plates 31. Fan hubs 4| to which the impellers 35 are secured extend freely through the central apertures of the plates 31, while the shaft 34 is suitably spaced from the edges of the apertures 38 through which air is admitted to the motor.

The motor chamber and air passage conduit is formed within the body 3| by a spirally wound wall or bafile 42, the outer terminal edge 43 of which is secured to the inner wall of the cylindrical body 3|, as shown at 44, by suitable means such as the bolt 45, which also secures one of the insulator and spacer elements hereinafter described. From the securement at 44, the wall is spiraled inwardly to terminate in an abruptly inturned portion 45 which bears against the motor. The side edges of the wall or baffl 42 are arranged to bear against and to seal and be secured to, if desired, the end walls of the cupshaped members 30.

By this arrangement it will be seen that there is formed a spiral passage of increasing cross sectional area extending from the motor in outwardly spiralling convolutions to the outlet aperture Adjacent the outlet H, the body members 3| are cut to form an outlet 4?, the material from which is bent upwardly to form an upper outlet guide flange 48 which is formed to contact the grill l8 at its upper edge to which it may be secured if desired. A lower outlet guide flange 59 is provided extending from the lower edge of the grill l8 to be secured as at to the outer convolution of the wall 42 and thus the members 49 and 49 provide terminal air guides for directing air from the spiral passage to the outlet I i.

For heating the air in its passage through the spiral there is provided an electrical resistance element 5|, the ends of which are connected to the conductors 52 and 53. The element 5| is arranged adjacent the outer or concave walls of the convolutions by its support from insulating spacers 54 which are mounted upon bolts 55 which are secured through the convolutions of the wall 42. The element is strung crosswise of the air passage in zig-zag fashion.

The resistance element 5| is of the usual type which in response to current passage therethrough becomes heated to the point of incandescence, thereby propagating the greater portion of its energy as radiant energy. Air coming in direct contact with the resistance will be heated by conduction, while the radiant energy will strike the wall of the baffle, thus heating the walls which in turn will heat the air by conduction.

An important feature of the present invention is the fact that the resistance element is wholly confined within the convolutions of the baffle so that no direct emanation of radiant energy through the outlet H is permitted and thus the preponderance of heating energy is transferred to the moving air without loss by emitted radiant heat. It will be seen that with the motor and resistance element both energized, a steady uniform and unidirectional flow of intensely heated air will emerge from the outlet with a minimum loss of energy by heat radiation and a maximum absorption of heat by the air in its traversal through the passageway.

While various circuit arrangements may be,

employed for the control of the motor and the heating element it is desirable that means be employed whereby the motor may be energized independently of the energization of the heating element. Two circuits by which this may be done are shown in Figs. 4 and 5. In each instance two switches are used, one of which may be mounted in each of the handle end securing members I9 and controlled by the actuating members 2 i.

Referring specifically to Fig. 4, current is supplied through a conductor 59 and a primary switch El which may be located within the end handle securing member [9 of the end housing l8. From the switch 5|, current leads directly to the motor 1V! to which is connected the return conductor 62. The heating element E is controlled by a separate switch 53 which may be located within the handle end member I9 of the opposite end housing ll. With this arrangement it will be readily seen that when the switch 6| is closed while the switch 63 remains open, the motor will be energized without energizetion of the element E and thus the device may be used as a simple air circulator. If both switches are simultaneously closed, the element E will be energized, while the motor is in operation so that the device acts as a hot air circulator or space heater. In this arrangement, it will be noted that the primary switch 6| is in the line in advance of the switch 63 so that it is impossible to inadvertentl energize the heating element without energizing the motor, thus guarding the device against accidental burning out of the heating coil.

It may also be desirable to provide for a varia tion in the energy supplied to the heating element and this may be accomplished by selectively energizing the heating element either in parallel or in series with the motor. Fig. 5 of the drawings illustrates a circuit arrangement for providing such selective energization. The input conductor 60 of Fig. 5 leads to a singlepole, double-throw switch 65, the contact 66 of which leads, directly to the motor which is directly connected with the return conductor 62.

Thejswitch 85 in this arrangement constitutes the primary switch which must be closed in one position or another to provide energization for either the motor or the heating element E. The secondary switch is indicated at 6? and is likewise a single-pole, double-throw switch. With this circuit when the switch 65 is moved to the contact 66 and with the switch 61 open, the motor will be energized, but there will be no energization with the heating element E. If, however, the switch 65 is closed with respect to contact 66 and the switch 67 is moved to the upper contact 68, current will flow through both the motor and the element E in parallel, the conductor 62 constituting a return circuit for both the motor and the element. With the switch 65 I closed with respect to contact 66 and the switch 6'! moved downwardly to the lower contact 69, no current will flow through the element E since the lower contact 69 is connected by conductor l with the contact ll associated with the switch 65.

If, however, the switch 65 is moved to engage contact H, current will flow iherethrough to conductor Hi and, switch being closed through the contact 69, current will flow through the element E and therefrom to the motor, the return being made through the conductor 52, thereby establishing a series circuit through the element and motor.

From a consideration of the circuit of Fig. 5, it will be seen that while it is impossible to energize the heating element without energization of the motor, it is possible to energize the motor without energizing the heating element so that the device may be actuated as a simple fan or blower. However, by a selective positioning of i the switches 65 and 67, it is possible to simultaneously energize both the motor and element either in parallel relation or in series relation.

From the foregoing, it will be seen that the present invention provides a novel, simple, efiicient, and economic device which, may be used 7 What I claim is:

1. In adevice of the character described, means constituting a spiral path of air travel of increasing cross sectional area having a plurality of contiguous convolutions, and heating means within the first-mentioned meansarranged in heat exchange relation with airtraversing the path formed by said first-mentioned means.

2. In a device of the character described including a convolute air passage of uniformly increasing cross section, an air inlet at the end of least cross section, an air outlet at the end of greatest cross section, and a heating element extending Within a major portion of said passage and terminating inwardly of any point from which a straight line may be projected outwardly through the outlet of said passage.

3. In a space heater, a casing, a fan chamber within said casing, a motor chamber in communication with said fan chamber, a convolute air passage communicating with said motor chamber, and a heating element mounted in said passage and wholly enclosed thereby.

4. In aspace heater, .a casing, a pair of fan chambers within said casing, a motor chamber within said casing between said fan chambers and communicating therewith, a convolute air passage communicating with said motor chamber, and a heating element mounted in said passage and wholly enclosed thereby.

5. In a device of the character described, a wall forming a spiral air passage having a plurality of contiguous turns, a heating element mounted insaid passage adjacent the concave side of said wall whereby air passing thereover will be heated by direct contact therewith and whereby the Wall will be heated so that the convex side of the wall in the adjacent turn may exchange heat with air passing thereover. 6; In a portable domestic space heater, a casing having air inlets, a motor-fan unit within said casing including a motor and a pair of fans op-- erable to draw air in through said inlets and to wards said motor, a convolute baflie within said casing and surrounding said motor, said ballie forming a convolute air passage of increasingly larger cross section away from said motor and including juxtaposed turns, an air outlet in the side of said casing in communication with the air passage formed by said bafiie, and an electrical resistance element. within said passage mounted on the wall formed by said bafile and comprising transverse runs of said element, said runs terminating at a point spaced from the outlet of the passage inwardly beyond any point from which a straight line may be projected through the outlet opening of the casing.

7. A self-contained portablespace heater com prising a casing having an air inlet and an air outlet, a motor disposed in said casing, a power shaft projecting from each end of said motor, a fan mounted on each end of said power shaft for rotation therewith whereby air will by the action of said fans be drawn through said inlet and discharged into the space around said motor, an air discharge passage defined by a pluralit of juxtaposed convolute walls, said passage communicating with the space around said motor and with said air outlet, the cross sectional area of which progressively increases from said space to said outlet, electrical heating means disposed within said passage and extending from adjacent said space to a position in advance of a straight line projected through said outlet whereby said heating means is invisible from the exterior of said heater and is in a position out of reach by a straight object inserted through said outlet,.said heating means being disposed adjacent one wall of the convolutions whereby said wall will be heated, the heat dissipating capacity of said heating means increasing as the cross sectional area of said passage increases whereby heat will be dissipated in proportion to the volume of air flowing therethrough, the path of air travel through the heater being such that heat generated through said motor will be dissipated thereto and additional heat will be dissipated thereto by said heating means and the heated walls of said passage.

8. A self-contained portable space heater coprising a casing having an air inlet and an air outlet, a motor disposed in said casing, a pair of fans operatively connected to said motor for rotation thereby whereby air will by the action of said fans be drawn through said inlet and discharged into the space around said motor and an air discharge passage communicating with the space around said motor and with said air outlet,

said passage being defined by a plurality of juxtaposed convolute walls, electrical heating means disposed within said passage adjacent one wall of the convolutions whereby said wall is heated, the path of air travel through the heater being such that heat generated by said motor will be dissipated thereto and additional heat will be dissipated thereto b said heating means and the heated Walls of said passage.

9. A self-contained portable space heater comprising a casing having an air inlet and an air outlet, a motor disposed in said casing, air moving means operatively associated with said motor whereby air will be drawn through said inlet and discharged into the space around said motor, an air discharge passage communicating with the space around said motor and with said air outlet, said passage being defined by a plurality of juxtaposed convolute Walls, electrical heating means disposed within said passage adjacent one wall of the convolutions whereby said wall is heated, the path of air travel through the heater 10 being such that heat generated by said motor will be dissipated thereto and additional heat will be dissipated thereto by said heating means and the heated walls of said passage common to adjacent convolutions.

ERIC C. WAI-ILBERG.

REFERENCES CITED The following references are of record in the 

